Solid gas generating compositions containing phosphate burning rate suppressants



2 ited States Pate 3,220,898 SOLID GAS GENERATING COMPOSITIONS CONTAINING PHOSPHATE BURNING RATE SUPPRESSANTS Robert H. Ossyra, Leon, N. Ortkiese, and Wayne A.

Proell, Seymour, Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Illinois No Drawing. Filed Aug. 20, 1963, Ser. No. 303,985

6 Claims. (Cl. 149-18) a combustion catalyst gives, such as low temperature ignitiability and combustion stability.

We have now discovered that the burning rate of gas generating compositions may be suppressed by themclusion in the composition of a miner amount of a phosphate or amidophosphate which does not contain atoms of metals (other than, of course, phosphorous). We have also discovered that the addition of such a phosphate imparts to the composition the characteristic of producing especially clean combustion exhaust gases.

The gas generating compositions to which this invention is applicable are those in which the main constituent is ammonium nitrate. The amount of ammonium nitrate will vary widely, but it is generally in the range of about 40 to 80%, advantageously in the range of 55-70%. Commercially available ammonium nitrate, preferably in a finely divided particulate form which may be produced by prilling or grinding, is suitable. The invention may also be used in the so-called double base propellants, in which the dominant constitutes are nitrocellulose and nitroglycerine.

In order to permit the shaping of the composition into definite configurations, a matrix former or binder material is incorporated into the composition. When ammonium nitrate decomposes, free oxygen is formed. Oxidizable organic materials are used as the binders in order to take advantage of the existence of free oxygen.

Suitable binder materials for gas generating compositions are well known in the art. Generally, the binder includes high molecular weight hydrocarbons, such as asphalt or residuums, and/ or a polymeric material, such as cellulose acetate, polyvinyl resins, including polyvinyl chloride and polyvinyl acetate, styrene-acrylonitrile, butadiene-styrene-acrylonitrile, polyurethanes, and natural or synthetic rubbers and elastomers. Frequently, a plasticizer component is included which is generally an oxygenated hydrocarbon. Illustrative plasticizers are referred to in US. Patent No. 3,067,075. Frequently, two or more plasticizers are used.

Suitable combustion catalysts include various organic and inorganic chromates, heavy metal cyanides, particcularly Prussian blues, and alkali metal barbiturates. Such combustion catalysts are desirably included in the compositions herein claimed; merely eliminating such catalysts generally will not produce an eflect comparable ice to that obtained by the inclusion of a phosphate or amidophosphate. Various burning rate promoters, such as finely divided carbon, which is not per se a combustion cataylst, are also frequently incorporated in gas generating compositions.

Frequently aromatic amines, such as toluene diamine and N-phenyl morpholine, may be used in minor amounts as gas evolution stabilization additives.

The phosphates which we have discovered are eiiective in minor amounts to suppress the burning rate of gas generating compositions, relative to the burning rate of a composition of the same ingredients in the same relative proportion but without having a phosphate, are those phosphates which are free of metal atoms, phosphorus not being considered as a metal in this sense. Preferably, the phosphates are those in which only phosphorous, oxygen, hydrogen, carbon and nitrogen atoms appear, although not necesarily all such atoms in each particular phosphate. Broadly speaking, the phosphates useful as burning rate suppressors are the organic esters and the ammonium and organic amine salts of either phosphoric acid or of amidophosphoric acids. Also included are mixed ester-amine salt phosphates and amidophosphates.

The organic esters of phosphoric acid are preferably diand tri-esters in which the ester radicals have not more than about 24 carbon atoms per radical, such as alkyl, naphthenyls, alkenyls and mono-nuclear aryls, including their non-hydrocarbon substituted derivaties wherein the substituents are hydroxyl, nitro and amine groups. The radicals forming phosphate esters may be uniform or mixed. Illustrative of radicals which may form the esters are ethyl, isopropyl, t-butyl, allyl, hexyl, cyclohexyl, bicyclohexyl, octyl, lauryl and stearyl, phenyl, biphenyl, dinitrophenyl, cresyl, and triphenylmethyl. The phosphate esters may also be mixed according to radical type, such as alkyl-aryl, and alkyl-naphthenyl. Illustrative specific organic ester phosphates are triphenyl phosphate, tricresyl phosphate, dicyclohexyl hydrogen phosphate, isopropyl or hexyl ditridecyl phosphate, trihexyl phosphate, ethyl distearyl phosphate, dibutyric hydrogen phosphate, and dioxyhexyl nitrotolyl phosphate.

Other suitable phosphates include the triamine salts of phosphoric acid, and the mono-or diamine salts of dior mono-esters of phosphoric acid. In addition, organic esters, amine salts or a mixed-ester amine salts of amidophosphoric acids may be used as burning rate suppressants.

Illustrative of amine salts of phosphoric acid are the salts formed by the reaction with phosphoric acid of methylamine, ethylamine, ethanol amine, hexylamine, aniline, pyridine, cyclohexylamine, and dior trimethylamine to yield phosphates of the type i (O-NI-IaR) and the amine salts of diesters, such as of di(tridecyl) hydrogen phosphate, propyl octyl hydrogen phosphate, palmyl dihydrogen phosphate, or of mono-esters. Illustrative amidophosphates are O-hexyl, O-lauryl N-lauryl amidophosphate, the ethylamine salt of O-isopropyl N- stearyl hydrogen amidophosphate, etc.

Cyclic esters of phosphoric acid and amidophosphoric acid may also be used, such as phenyl 1,3-propyl phosphate, methyl 1,2-(butyl-4-methoxy) phosphate, triphenylmethyl 1,2-propyl phosphate, and diisopropyl N,N-ethylene amidophosphate.

Additional illustrative phosphates and means of preparing them are known in literature; see, for instance, Van Wazers Phosphorus and Its Compounds (1958, Interscience Publishers, Inc.), Kirk-Othmers Encyclopedia Having thus described the invention, what is claimed is:

1. In a solid gas generating composition which comprises more than about 50% ammonium nitrate, the imof Chemical Technology, volume 10 (1953), and Wood- 5 provement of incorporating a member selected from the stocks US. Patent No. 2,406,423. class consisting of ammonium salts, organic amine salts The underlying chemical common denominator of the and organic esters of phosphoric acid and amidophoscompounds which have proven useful as burning rate phoric acids, and mixtures thereof, said esters and organic suppressors is the presence of a structure amine salts consisting of carbon, hydrogen, nitrogen,

O oxygen and phosphorous atoms and having less than {I about 24 carbon atoms per molecule, in an amount l sufiicient to decrease the burning rate of said composition in which the three single valences or bonds of the phosgi g i i of the same mgredlents having phorus atoms are connected to oxygen in an ester or p 2 h amine salt form or to nitrogen in the amido form. n a S01 gas generatmg composltlori W 16 i only Small amounts of the phosphate burning rate prises more than about 50% ammonium nitrate, the imsuppressor need be used generally in the range of about provement; i mcorporatmg a member selqcted f.rom the 0 2 to 10% advantageously in the range of about 0.5 to class consl.stmg of ammomum i 9rgamc amine salts 2 or 3% based on total Weight of the composition. 20 and i esters.of phosphonc q and ilmldophos' The phoshate may be added to the Composition in the phone acids and mixtures thereof, said organic salts and form of a liquid or solid; if solid, preferably in powdered esters.havm.g more than about carbon atoms per or granulated fomh The Sequence of phosphate addition organic radical, in an amount sufficient to decrease the is not critical to its effectiveness but the phosphate burning rate of said composition relative to a composition should be substantially uniformly dispersed throughout of the Safne mgredlents havmg no Phosphate Sald P the composition. phate being free of metal atoms.

A number of phosphate-containing gas generating com- T composltlon 0f clalm 1 Whefeln 531d member positions h b t t d to d t i th i burning is a trialkyl ester phosphate in which at least one of the rate constants and pressure exponents. The composialkyl groups has from 1 to about 8 carbon atoms and tions and test data are set forth in the table:

Table Grain No 1 2 3 4 5 6 7 Constituents Composition, Weight percent Acetyl triethyl citrate 11.9 11.85 11.8 11.8 11.5 12.5 9.15 Ammonium Nitrate. 62.5 62.30 60.0 60.0 60.0 60.0 67.35 Carbon 3.0 3.0 3.0 2.0 3.0 1.0 3. 52 Cellulose acetate 10.5 10.4 12.4 12.3 12.0 12.0 8.94 Dinitrophenoxy ethano 10.6 10. 10.8 11.4 10.5 11.0 9. 04 N-phenyl morpholine 0. 1 0. 5 0. 5 0. 5 0. 5 0. 5 0. 10 Sodium barbiturate 0.5 1.0 0.5 0.5 0.5 0.5 0. Toluene diamine 0.9 0. 5 0. 5 0. 5 0. 5 0. 5 0.90 Phosphate compound 0 0 0. 5 1. 0 1. 5 2. 0 0.50

Test Results Pressure exponent .59 .65 .63 .65 .65 .73 0. 65 Burning rate, inches/second:

At 1,000 p.s.i 0.066 .082 0. 043 .038 0.038 0.037

At 700 p.s.i 0.058

I Probably containing a minor amount of dinitrophenoxy ethyl ether. 2 Includes 0.25% graphite.

Grain Nos. 1 and 2 are blanks, and contain no phosphate additive. The phosphate compound of Grains Nos. 3, 4 and 5 was the diethanolic amine salt of di-tridecyl hydrogen phosphate, which may be made by neutralizing with diethanolic amine ((HOCH CH NH) the product obtained by partially esterifying phosphoric acid with tridecyl alcohol. The phosphorous compound of Grain No. 6 was the lauryl amine salt of O-ethyl, N-lauryl hydrogen amidophosphate. The phosphorus compound of Grain No. 7 was tricresyl phosphate.

The table shows that the addition of small amounts of the phosphate compounds substantially reduced the burning rate of the gas generating grains relative to substantially similar compositions in which no phosphate additive was incorporated. A particularly advantageous feature of the invention resides in the fact that the exhaust combustion gases of the phosphate containing grains were cleaner than when no phosphate was used. This was determined visually by inspection of the turbine blades against which the exhaust gases were impinged.

The burning rate tests were conducted in a Crawford bomb at about 25 C.

References Cited by the Examiner UNITED STATES PATENTS 2,969,638 1/1961 Sammons 14919 3,000,715 9/ 1961 Lawrence 14919 3,027,282 3/ 1962 Sammons 14919 3,027,284 3/ 1962 Sammons 149-19 3,087,844 4/1963 Hudson et a1. 14919 3,116,186 12/1963 Paul 14919 CARL D. QUARFORTH, Primary Examiner. 

1. IN A SOLID GAS GENERATING COMPOSITION WHICH COMPRISES MORE THAN ABOUT 50% AMMONIUM NITRATE, THE IMPROVEMENT OF INCORPORATING A MEMBER SELECTED FROM THE CLASS CONSISTING OF AMMONIUM SALTS, ORGANIC AMINE SALTS AND ORGANIC ESTERS OF PHOSPHORIC ACID AND AMIDOPHOSPHORIC ACIDS, AND MIXTURES THEREOF, SAID ESTERS AND ORGANIC AMINE SALTS CONSISTING OF CARBON, HYDROGEN, NITROGEN, OXYGEN AND PHOSPHOROUS ATOMS AND HAVING LESS THAN ABOUT 24 CARBON ATOMS PER MOLECULE, IN AN AMOUNT SUFFICIENT TO DECREASE THE BURNING RATE OF SAID COMPOSITION RELATIVE TO A COMPOSITION OF THE SAME INGREDIENTS HAVING NO PHOSPHATE. 